Drugs may be delivered to patients by a variety of methods including oral, intravenous, intramuscular, inhalation, topical, subcutaneous delivery or delivery directly or locally to the treatment site (e.g., intrathecally, intraspinally, intraarticularly, etc.). The method of delivery chosen depends, among other things, upon the condition being treated, desired therapeutic concentration of the drug to be achieved in the patient and the duration of drug concentration that must be maintained.
Recently, drug depots have been developed which allow a drug to be introduced or administered to sites beneath the skin of a patient so that the drug is slowly released over a long period of time. Such drug depots allow the drug to be released from the depot in a relatively uniform dose over weeks, months or even years. This method of administering drugs is becoming especially important and popular in modulating the immune, inflammation and/or pain responses in treatment of chronic conditions including rheumatoid arthritis, osteoarthritis, sciatica, carpal tunnel syndrome, lower back pain, lower extremity pain, upper extremity pain, cancer, tissue pain and pain associated with injury or repair of cervical, thoracic, and/or lumbar vertebrae or intervertebral discs, rotator cuff, articular joint, TMJ, tendons, ligaments, muscles, and the like.
Previously, drug depots and other types of implants have been inserted into the treatment site beneath the skin by use of a trocar device, which is a two-piece device that includes a cannula and an obdurator. The trocar device requires an incision to be made through the skin at the site of implant of the drug depot using a separate instrument (e.g., scalpel). A cannula and obdurator are inserted together through the skin at the incision site. Next, the obdurator is withdrawn, leaving the cannula in place as a guide for inserting the drug depot. The drug depot is inserted through the cannula, and the obdurator is used to push the implant to the end of the cannula. The cannula and obdurator are then withdrawn completely, leaving the implant in place beneath the skin.
Typically, trocar devices are used to implant drug depots subcutaneously over a large area (e.g., 2-2.5 inches), with a typical drug depot in the order of 1½ inches long. Thus, the trocar device is not suitable for many treatment sites because it lacks precision and may cause additional trauma to the tissue surrounding the site of implant.
Other drug delivery devices have been developed to simplify implanting the drug depots. These devices have a handle for one-handed implantation of the drug depot, a needle containing the drug depot to be implanted and a rod positioned within the needle for pushing the drug depot out of the needle. Once the needle containing the drug depot has been inserted at the site of implant, a spring loaded trigger on the handle is activated which causes the needle to be automatically withdrawn by a spring leaving the implanted drug depot in place. Unfortunately, it is not possible to control the motion of the needle in these devices because the needle will automatically retract upon activation of the trigger. The complex spring loaded propelling system and trigger of these devices increase the chances that the device will jam and fail to eject the drug depot when required.
Conventional needle and syringe devices have been used to implant a drug depot to sites such as, for example, the epidural space. These devices typically utilize a syringe preloaded with the drug depot and an epidural needle. The needle is inserted through the skin, supraspinus ligament, intraspinus ligament, ligamentum flavum and then into the epidural space. The drug depot is delivered through the needle to the epidural space using the syringe plunger. Conventional needle and syringe devices often do not easily allow controlled and precision implant of the drug depot. If multiple drug depot implants are needed, these conventional needle and syringe devices often do not allow accurate placement of the implant in a manner so that one drug depot does not substantially interfere with the dissolution of the other.
In certain methods of drug depot implantation, the drug depots are secured in the drug cartridge by use of a bulking agent. The bulking agent may be added to the drug depot to ensure the drug depot is secure within the chamber, such that the drug depot is released when a plunger is engaged to dislodge the drug depot from the cartridge. The bulking agent is sometimes added to the drug chamber before the drug depot is added to the chamber. Other times the drug depot is added to the drug chamber first and then the drug depot is added to the chamber. Use of a bulking agent to retain the drug depot in a drug cartridge requires additional steps and is time consuming. Thus, a drug delivery device which reduces a need for use of bulking agents is needed.
New drug delivery devices are needed, which can easily allow accurate and precise implantation of a drug depot with minimal physical and psychological trauma to a patient. When implanting several drug depots, a drug delivery device is needed that accurately and precisely allows placement of the drug depot in a manner such that one depot does not substantially interfere with the dissolution of the others.